1. American College of
Preventative Medicine
February 23, 2008
Austin, TX
Robert S. Webb
NOAA ESRL Climate Analysis Branch
formerly the Climate Diagnostics Center (CDC)
Boulder, Colorado
An Introduction to
Global Climate Change
2. Overview
• Global Climate Change:
Trends & Projections
• North America:
Trends & Projections
• Parting Thoughts
3. What is Climate
Climate is the aggregated pattern of weather,
meaning averages, extremes, timing, spatial
distribution of…
• hot & cold
• cloudy & clear
• humid & dry
• drizzles & downpours
• snowfall, snowpack, & snowmelt
• blizzards, tornadoes, & typhoons
Climate change means altered patterns.
Global average temperature is just one measure of the
state of the global climate as expressed in these patterns.
Small temperature changes big changes in the patterns.
(after Holdren NCES, 2008)
5. Global Temperatures are increasing
Green bars show 95%
confidence intervals
the 15 hottest years all occurred since 1990
http://data.giss.nasa.gov/gistemp/graphs/
7. Historic record of global climate change
Warming of the climate
system is unequivocal,
as is now evident from
observations of increases
in global average air and
ocean temperatures,
widespread melting of
snow and ice, and rising
global mean sea level.
8. Warm nights increasing
Cold nights decreasing
Frequency of occurrence of cold or warm temperatures for 202
global stations for 3 time periods:1901 to 1950 (black), 1951 to
1978 (blue) and 1979 to 2003 (red).
9. Proportion of extreme precipitation events
increasing in most areas
NH Winter NH Summer
The frequency of heavy precipitation events has increased over most
land areas - consistent with warming and increases of atmospheric
water vapor while more intense and longer droughts have been
observed since the 1970s, particularly in the tropics and subtropics.
10. Greenhouse gas concentrations
Compared to natural
changes over the past
10,000 years, the spike in
concentrations of CO2 &
CH4 in the past 250 years is
extraordinary.
Humans are responsible for
the recent dramatic
increase emissions. Fossil
CO2 & CH4 lack carbon-14,
and the observed drop in
atmospheric C-14 is
measurable.
(IPCC AR4 WG1, 2007)
12. Ranges of projected surface warming
multi-model averages for different emission
scenarios and assessed ranges of warming
(IPCC AR4, 2007)
13. Projected surface temperature changes
for the early and late 21st century
relative to the period 1980–1999
Continents Warm 50% more than oceans
14. Observed & simulated continental & global
scale changes in surface temperature
observed change
(black line);
climate models
simulations using
natural (blue) and
anthropogenic
(red) forcings
15. Projected percent changes in precipitation
for the period 2090–2099
(relative to 1980–1999)
Warmer climate More Water Vapor in the atmosphere
but an expanded belt of subtropical aridity
NH Winter NH Summer
17. Observed trends in some biophysical and
socio-economic indicators in North America
(IPCC WG1, 2007)
18. Changes in the
percent of days in
a year above
three thresholds
for North America
for daily high (top)
and low (bottom)
temperature
CCSP SAP 3.3
19. U.S. national average “heat wave” index
defined as warm spells of 4 days in duration with mean
temperature exceeding the threshold for a 1 in 10 year event
CCSP SAP 3.3
20. Area of the U.S. with much above normal
daily high and low summer temperatures
CCSP SAP 3.3
21. Regions in where heavy and very heavy
precipitation has increased
CCSP SAP 3.3
29. Emerging Challenges
Pythons could squeeze lower third of USA
Feb 21, 2008 By Elizabeth
Weise, As climate change
warms the nation, giant
Burmese pythons could
colonize one-third of the USA,
from San Francisco across
the Southwest, Texas and the
South and up north along the
Virginia coast, according to
U.S. Geological Survey maps
released Wednesday.The
pythons can be 20 feet long
and 250 pounds. They are
highly adaptable to new
environments.
Current Range Projected Range ca. 2100
